design and the mechanism of controlling a robotic arm by noor ali al teef yousef sofyan jghef hasan...
TRANSCRIPT
I
Syrian Private University
Faculty of Computer & Informatics
Engineering
Design and the mechanism of
controlling a robotic arm
A Senior Project Presented to the Faculty of Computer and
Informatics Engineering In Partial Fulfillment of the Requirements
for the Degree
Of Bachelor of in Communication & Network Engineering
Under the supervision of
Prof. Ahmad Rateb Al-Najjar
Prof. Ali Skaff
II
By
Noor Ali Al teef
Yousef Sofyan Jghef
Hasan Mohamed Heddeh
Mohamed Zaki Hani Ibrahim
Mohammed Ali Ismail Abdul Rahman
August 2015
©2015 - ALL RIGHTS RESERVED
CERTIFICATION OF APPROVAL
III
Prof. Ahmad Rateb Al-Najjar Date :
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Prof. Ali Skaff Date :
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IV
CONTENT
Table of Figure .................................................................................................................. VI
CHAPTER 1: INTRODUCTION ....................................................................................... 2
CHAPTER 2: DESIGNING PORTION ............................................................................. 3
2.1 Design Of Robotic Arm ............................................................................................ 3
2.2 Five degrees of freedom ............................................................................................ 4
2.3 Positive and negative on robotic arm ........................................................................ 5
2.3.1 The Positive : ...................................................................................................... 5
2.3.2 The negative : ..................................................................................................... 6
CHAPTER 3: THEORETICAL PORTION ....................................................................... 7
3.1 Arduino...................................................................................................................... 7
3.2 Specifications ............................................................................................................ 8
3.3 Programming ............................................................................................................. 9
3.4 Power ......................................................................................................................... 9
3.5 Memory ................................................................................................................... 10
3.6 Arduino development "IDE" ................................................................................... 11
CHAPTER 4: PRACTICAL PORTION ........................................................................... 13
4.1 Servo Motors ........................................................................................................... 13
4.2 Theory of DC Servo Motor ..................................................................................... 15
4.3 Separately Excited DC Servo Motor ....................................................................... 15
4.3.1 DC Servo Motor Theory : ................................................................................. 15
Field Controlled DC Servo Motor Theory ................................................................ 16
4.3.2 Armature Controlled DC Servo Motor Theory: ............................................... 18
4.3.3 Permanent Magnet DC Servo Motor : .............................................................. 19
4.4 Deriving State Equations for a DC Servo Motor .................................................... 19
V
4.4.1System Model : .................................................................................................. 19
4.4.2 Developing The State Equations : .................................................................... 20
4.5 Potentiometers ......................................................................................................... 22
4.6 Bluetooth HC-06 module ........................................................................................ 23
4.7 Specifications .......................................................................................................... 24
4.7.1 Hardware features ............................................................................................. 24
4.7.2 Software features .............................................................................................. 24
CHAPTER 5: MECHANICAL PORTION ...................................................................... 28
5.1Mechanical Design ................................................................................................... 29
5.2 Driving engines using complementary angle .......................................................... 34
5.3 Robot Arm Control.................................................................................................. 34
5.4 End-Effector Selection ............................................................................................ 35
5.5 MIT App Inventor ................................................................................................... 36
5.6 Robotic arm app using MIT app inventor ............................................................... 37
5.6.1 Interface designer : ........................................................................................... 39
5.6.2 Interface Blocks: ............................................................................................... 40
5.6.3 App Designer: ................................................................................................... 40
5.6.4 Arm Block Diagram: ........................................................................................ 41
CONCLUSION ................................................................................................................. 43
REFERENCE .................................................................................................................... 44
Appendix A ....................................................................................................................... 46
VI
Table of Figure
Figure2.1 shows the image of a servo motor 4
Figure2.2 Five degrees of freedom 4
Figure2.3 Robot Arm 5
Figure3.1 Arduino Uno microcontroller board (interface) 7
Figure 3.2 Arduino Uno microcontroller board(back view) 8
Figure 3.3 Arduino Power Supply 10
Figure 3.4 ATmega328P – Memory 10
Figure 3.5 Interface Arduino Uno Program 11
Figure 4.1 Big Servo Motor 13
Figure 4.2 G9 Servo Motor 14
Figure 4.3 Block diagram of a Servo motor 14
Figure 4.4 Separately Excited DC Servo Motor 15
Figure 4.5 Field controlled DC servo motor 16
Figure 4.6 knee point of magnetizing saturation curve 17
Figure 4.7 knee point of magnetizing saturation 18
Figure 4.8 The terms Ra and La are the resistance 20
Figure 4.9 Simulation Diagram For The DC Servo Motor 21
Figure 4.10 A Potentiometer 22
Figure 4.11 Circuit Diagram of a Potentiometer 23
Figure 4.12 Bluetooth HC.06 module (Front View) 24
Figure 4.13 Bluetooth HC.06 module(Back View) 24
VII
Figure 5.1 Free body diagram of the robot arm 26
Figure 5.2 Work region of the robotic arm 27
Figure 5.3 Force diagram of robot arm 27
Figure 5.4 Force diagram of link CB 28
Figure 5.5 Two Type Of Servo Motor 30
Figure 5.6 Electronic scheme of control 32
Figure 5.7 gripper Closed , gripper Open 33
Figure 5.8 MIB Structure 34
Figure5.9 Interface designer 36
Figure5.10 Interface Blocks 37
Figure 5.11 App Designer 38
Figure 5.12 Arm Block Diagram 39
1
الملخص باللغة العربية
ضووم ل تمحووت الدرا د ووحلدرح روووحلحووتولتموومورلت ميووحلم دصليروووحرلتوورلتموومورلدرووم دصلد روووحل اوو ل لا ووو رلت م وو و خموودلا يوو الموو لدرح وووحلتتوورلتمتوووال ل وو رمهات لرتسيووملدرمٍوو رلدر وووهحل لوو و
اال مح و ال تدرتوولتووترل اماووحلل وو فتمركلفون لدرمو االدرخفوفوحلدره واوحلدرتوولت وتلدروم دصلد رووحلمومتادرمح وو التاووكلراووو لدروو هل ووو لد،م صإلل ةضوو فحلدروو لتااوووحلح وو الدرووم دصرلد لدرمووتح رلدرووم لووووتال
لدروا ال ا لتااوولدرتضاوحر
ووووتخادرل ميوووووحللATMEGA-328pتووووترل ماوووووحلدرت يمووووحل اوووو لدرمووووتح رلموووو لسووووتص سمهلArduinoووواحلدرووو ل رلووووترلد وووتخادرلموووو وودلدريٍوووالعوضووو ةلرا لووو ل ووو لمدتووووحلدروووات دالتدةلووو دالدرم
يٍ ملعسا توارلففول ررلدروترإللت وو لع للوم لدرمتح ررل ةم لدرتح رل رم دصلد روحلعوض ةل تخادرلدرم دصلد روحلي ر حلراسفعلدرا ررل ةض فحلدر لدر ت تتو التد،تمتوحإللفون للوم لد،سوتدصلمو لد،م صلتمتو مل
ل تستصلته وو تٍ لدرمت ححلفول االمي الالعخ ىر
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2
CHAPTER 1: INTRODUCTION
A Robot is a virtually intelligent agent capable of carrying out tasks robotically with the
help of some supervision. Practically, a robot is basically an electro-mechanical machine
that is guided by means of computer and electronic programming. Robots can be
classified as autonomous, semiautonomous and remotely controlled. Robots are widely
used for variety of tasks such as service stations, cleaning drains, and in tasks that are
considered too dangerous to be performed by humans. A robotic arm is a robotic
manipulator, usually programmable, with similar functions to a human arm.
This Robotic arm is programmable in nature and it can be manipulated. The robotic arm
is also sometimes referred to as anthropomorphic as it is very similar to that of a human
hand. Humans today do all the tasks involved in the manufacturing industry by
themselves. However, a Robotic arm can be used for various tasks such as welding,
drilling, spraying and many more. A self-sufficient robotic arm is fabricated by using
components like micro-controllers and motors. This increases their speed of operation
and reduces the complexity. It also brings about an increase in productivity which makes
it easy to shift to hazardous materials. The main part of the design is ATMEGA-328p
micro-controller which coordinates and controls the product’s action. This specific micro
controller is used in various types of embedded applications. Robotics involves elements
of mechanical and electrical engineering, as well as control theory, computing and now
artificial intelligence. According to the Robot Institute of America, ―A robot is a
reprogrammable, multifunctional manipulator designed to move materials, parts, tools or
specialized devices through variable programmed motions for the performance of a
variety of tasks.
The robots interact with their environment, which is an important objective in the
development of robots. This interaction is commonly established by means of some sort
of arm and gripping device or end effectors. In the robotic arm, the arm has a few joints,
similar to a human arm, in addition to shoulder, elbow, and wrist, coupled with the finger
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joints; there are many joints . The design process is clearly explained in the next section
with detailed information regarding the components which are used.
CHAPTER 2: DESIGNING PORTION
2.1 Design of Robotic Arm
The Robotic Arm is designed using the Microcontroller i.e. ATMEGA328p
Micro-controller using Arduino programming. This process works on the principle of
interfacing servos and potentiometers. This task is achieved by using Arduino board.
Potentiometers play an important role The remote is fitted with potentiometers and the
servos are attached to the body of the robotic arm. The potentiometer converts the
mechanical motion into electrical motion. Hence, on the motion of the remote the
potentiometers produce the electrical pulses, which are in route for the Arduino board.
The board then processes the signals received from the potentiometers and finally,
converts them into requisite digital pulses that are then sent to the servomotors. This
servo will respond with regards to the pulses which results in the moment of the arm.
Figure 2.1 shows the image of a servo motor. It consists of a motor which is
coupled to a sensor, used for position feedback, through a reduction gearbox. It also
accompanies a relatively sophisticated controller, usually a dedicated module designed
specifically for use with servo motors
In short, the micro controller interfaces all these components specified below. A
short list of components include
1. Servo motors
2. Potentiometers
3. Atmega 328p.
4. Arduino Deumilanove "IDE"
5. Bloutooth module.
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Figure2.1 shows the image of a servo motor
2.2 Five degrees of freedom
Serial and parallel manipulator systems are generally designed to position an end-
effector with five degrees of freedom, consisting of three in translation and tow in
orientation. This provides a direct relationship between actuator positions and the
configuration of the manipulator
Figure2.2 Five degrees of freedom
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Robot arms are described by their degrees of freedom. This number typically
refers to the number of single-axis rotational joints in the arm, where higher number
indicates an increased flexibility in positioning a tool. This is a practical metric, in
contrast to the abstract definition of degrees of freedom which measures the aggregate
positioning capability of a system.
Figure2.3 Robot Arm
2.3 Positive and negative on robotic arm
2.3.1 The Positive:
Increase productivity
Use equipment effectively
Reduce working costs
Flexibility at work
Get the job done in the shortest time
Provide good returns on investment
Better accuracy in performance
Ability to work in risky ways and make it more safe
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2.3.2 The negative:
Cause unemployment for manual workers
High initial cost
designed Arm to perform specific tasks and not comparable to
the human hand
Difficulty programmed to perform Accurate tasks
Needed a large number of sensors and high accuracy to perform the
Complex tasks
And other technical problems, "especially in the fields of artificial
intelligence and Machine vision" .
When the Robotic arm break down the production line will go off in the
factories.
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CHAPTER 3: THEORETICAL PORTION
3.1 Arduino
Arduino Uno is a microcontroller board based on the ATmega328P . It has 14
digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16
MHz quartz crystal, a USB connection, a power jack and a reset button. It contains
everything needed to support the microcontroller; simply connect it to a computer with a
USB cable or power it with a AC-to-DC adapter or battery to get started.. You can tinker
with your UNO without worrying too much about doing something wrong, worst case
scenario you can replace the chip for a few dollars and start over again.
Figure3.1 Arduino Uno microcontroller board (interface)
"Uno" means one in Italian and was chosen to mark the release of Arduino
Software (IDE) 1.0. The Uno board and version 1.0 of Arduino Software (IDE) were the
reference versions of Arduino, now evolved to newer releases. The Uno board is the first
in a series of USB Arduino boards, and the reference model for the Arduino platform; for
an extensive list of current, past or outdated boards see the Arduino index of boards.
8
Figure 3.2 Arduino Uno microcontroller board (back view)
3.2 Specifications
Microcontroller ATmega328P
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
PWM Digital I/O Pins 6
Analog Input Pins 6
DC Current per I/O Pin 20 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega328P)
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of which 0.5 KB used by bootloade*r
SRAM 2 KB (ATmega328P)
EEPROM 1 KB (ATmega328P)
Clock Speed 16 MHz
Length 68.6 mm
Width 53.4 mm
Weight 25 g
3.3 Programming
The Arduino Uno can be programmed with the (Arduino Software (IDE)).The
ATmega328 on the Arduino Uno comes preprogrammed with a bootloader that allows
you to upload new code to it without the use of an external hardware programmer. It
communicates using the original STK500 protocol.
3.4 Power
The Arduino Uno board can be powered via the USB connection or with an
external power supply. The power source is selected automatically.
External (non-USB) power can come either from an AC-to-DC adapter (wall-
wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug
into the board's power jack. Leads from a battery can be inserted in the GND and Vin pin
headers of the POWER connector.
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Figure 3.3 Arduino Power Supply
3.5 Memory
The ATmega328 has 32 KB (with 0.5 KB occupied by the bootloader). It also has
2 KB of SRAM and 1 KB of EEPROM
Figure 3.4 ATmega328P – Memory
6%
89%
3%
2%
SRAM - 2 Killobyte
Flash Disk - 29 Killobyte
EEPROM - 1 Killobyte
Bootloader 0.5 Killobyte
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3.6 Arduino development "IDE"
The Arduino integrated development environment (IDE) is a cross-platform
application written in Java, and is derived from the IDE for the Processing programming
language and the Wiring projects. It is designed to introduce programming to artists and
other newcomers unfamiliar with software development. It includes a code editor with
features such as syntax highlighting, brace matching, and automatic indentation, and is
also capable of compiling and uploading programs to the board with a single click. There
is typically no need to edit make files or run programs on a command-line interface
Figure 3.5 Interface Arduino Uno Program
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Developer(s) Arduino Software
Stable release 1.0.3 / December 10, 2012; 3months
ago
Written in Java, C and C++
Operating system Cross-platform
Type Integrated development environment
Website arduino.cc
Arduino programs are written in C or C++ The Arduino IDE comes with a software
library called "Wiring" from the original Wiring project, which makes many common
input/output.
Operations much easier. Users only need define two functions.
To make a runnable cyclic executive program:
Setup (): a function run once at the start of a program that can initialize settings.
Loop (): a function called repeatedly until the board powers off.
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CHAPTER 4: PRACTICAL PORTION
4.1 Servo Motors
Servo refers to an error sensing feedback control which is used to correct the
performance of a system. Servo or RC Servo Motors are DC motors equipped with a
servo mechanism for precise control of angular position.
The RC servo motors usually have a rotation limit from 90° to 180°. But servos do not
rotate continually. Their rotation is restricted in between the fixed angles.
The Servos are used for precision positioning. They are used in robotic arms and legs,
sensor scanners and in RC toys like RC helicopter, airplanes and cars.
The specifications for big Servomotor used are as follows:
Weight- 55g
Dimension- 40.7*19.7*42.9mm
Stall torque- 10kg/cm
Operating speed-0.20sec/60degree(4.8v)
Operating voltage 4.8-7.2V.
Temperature range 0-55 degrees.
Figure 4.1 Big Servo Motor
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The specifications for small Servomotor G9 used are as follows:
Weight: 9 g
Dimension: 22.2 x 11.8 x 31 mm approx.
Stall torque: 1.8 kgf·cm • Operating speed: 0.1 s/60 degree
Operating voltage: 4.8 V (~5V)
Dead band width: 10 µs
Temperature range: 0 ºC – 55 ºC
Figure 4.2 G9 Servo Motor
Figure 4.3 Block diagram of a Servo motor
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4.2 Theory of DC Servo Motor
As we know that any electrical motor can be utilized as servo motor if it is
controlled by servomechanism. Likewise, if we control a DC motor by means of
servomechanism, it would be referred as DC servo motor. There are different types of
DC motor, such shunt wound DC motor, series DC motor, Separately excited DC motor,
permanent magnet DC motor, Brushless DC motor etc. Among all mainly separately
excited DC motor, permanent magnet DC motor and brush less DC motor are used as
servo.
4.3 Separately Excited DC Servo Motor
Figure (4.4) shows the block diagram of the separately excited Dc servo motor
Figure 4.4 Separately Excited DC Servo Motor
4.3.1 DC Servo Motor Theory:
The motors which are utilized as DC servo motors, generally have separate DC
source for field winding and armature winding. The control can be archived either by
controlling the field current or armature current. Field control has some specific
advantages over armature control and on the other hand armature control has also some
specific advantages over field control. Which type of control should be applied to the DC
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servo motor, is being decided depending upon its specific applications. Let's discus DC
servo motor working principle for field control and armature control one by one.
Field Controlled DC Servo Motor Theory
The Figure below illustrates the schematic diagram for a field controlled DC
servo motor. In this arrangement the field of DC motor is excited be the amplified error
signal and armature winding is energized by a constant current source
Figure 4.5 Field controlled DC servo motor
The field is controlled below the knee point of magnetizing saturation curve. At
that portion of the curve the MMF linearly varies with excitation current. That means
torque developed in the DC motor is directly proportional to the field current below the
knee point of magnetizing saturation curve.
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Figure 4.6 knee point of magnetizing saturation curve
From general torque equation of DC motor it is found that, torque T ∝ φIa.
Where, φ is field flux and Ia is armature current. But in field controlled DC servo motor,
the armature is excited by constant current source , hence Ia is constant here. Hence, T ∝
φ
As field of this DC servo motor is excited by amplified error signal, the torque of
the motor i.e. rotation of the motor can be controlled by amplified error signal. If the
constant armature current is large enough then, every little change in field current causes
corresponding change in torque on the motor shaft.
The direction of rotation can be changed by changing polarity of the field.
The direction of rotation can also be altered by using split field DC motor, where
the field winding is divided into two parts, one half of the winding is wound in clockwise
direction and other half in wound in anticlockwise direction. The amplified error signal is
fed to the junction point of these two halves of the field as shown below. The magnetic
field of both halves of the field winding opposes each other. During operation of the
motor, magnetic field strength of one half dominates other depending upon the value of
amplified error signal fed between these halves. Due to this, the DC servo motor rotates
in a particular direction according to the amplified error signal voltage.
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The main disadvantage of field control DC servo motors, is that the dynamic
response to the error is slower because of longer time constant of inductive field circuit.
The field is an electromagnet so it is basically a highly inductive circuit hence due to
sudden change in error signal voltage, the current through the field will reach to its steady
state value after certain period depending upon the time constant of the field circuit. That
is why field control DC servo motor arrangement is mainly used in small servo motor
applications.
The main advantage of using field control scheme is that, as the motor is controlled by
field. The controlling power requirement is much lower than rated power of the motor.
4.3.2 Armature Controlled DC Servo Motor Theory:
Figure (4.5) shows the schematic diagram for an armature controlled DC servo
motor. Here the armature is energized by amplified error signal and field is excited by a
constant current source .
The field is operated at well beyond the knee point of magnetizing saturation
curve. In this portion of the curve, for huge change in magnetizing current, there is very
small change in mmf in the motor field. This makes the servo motor is less sensitive to
change in field current. Actually for armature controlled DC servo motor, we do not want
that, the motor should response to any change of field current.
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Figure 4.7 knee point of magnetizing saturation
Again, at saturation the field flux is maximum. As we said earlier, the general
torque equation of DC motor is, torque T ∝ φIa. Now if φ is large enough, for every little
change in armature current Ia there will be a prominent changer in motor torque. That
means servo motor becomes much sensitive to the armature current.
As the armature of DC motor is less inductive and more resistive, time constant of
armature winding is small enough. This causes quick change of armature current due to
sudden change in armature voltage.
That is why dynamic response of armature controlled DC servo motor is much
faster than that of field controlled DC servo motor.
The direction of rotation of the motor can easily be changed by reversing the polarity of
the error signal.
4.3.3 Permanent Magnet DC Servo Motor:
Field control is not possible in the case of permanent magnet DC motor as the
field is a permanent magnet here. DC servo motor working principle in that case is
similar to that of armature controlled motor.
4.4 Deriving State Equations for a DC Servo Motor
4.4.1System Model:
A useful component in many real control systems is a permanent magnet DC servo
motor. The input signal to the motor is the armature voltage Va(t), and the output signal
is the angular position θ(t). A schematic diagram for the motor is shown in Figure.
(4.4.1.1). The terms Ra and La are the resistance and inductance of the armature winding
in the motor, respectively. The voltage Vb is the back EMF generated internally in the
motor by the angular rotation. J is the inertia of the motor and load (assumed lumped
together), and B is the damping in the motor and load relative to the fixed chassis.
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Figure 4.8 The terms Ra and La are the resistance
The equations for the electrical side of the system are
Va(t) = Raia(t) + La dia(t)/dt + Vb(t) with Vb(t) = Kb dθ(t) /dt (1)
Va(t) = Raia(t) + La dia(t)/ dt + Kb dθ(t) /dt (2)
Where Kb is the motor’s back EMF constant. The equations for the mechanical side of
the system are
J d2θ(t)/ dt2 + B dθ(t)/ dt = Tapp(t) with Tapp(t) = KT ia(t) (3)
J d2θ(t)/ dt2 + B dθ(t)/ dt = KT ia(t) (4)
Where Tapp is the applied torque, and KT is the torque constant that relates the torque to
the armature current.
4.4.2 Developing the State Equations:
Here are three derivative terms in the system model for the DC servo motor—first
derivative of ia(t) in Eqn. (2) and first and second derivatives of θ(t) in Eqn. (4).
Therefore, there are a total of 3 state variables in the state space model. Although the first
derivative of θ(t) appears in both of those equations, it is the same variable and so does
not add an additional state variable. A simulation diagram can be drawn for this system
by solving Eqns. (2) and (4) for the highest derivative term in each. This yields the
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expressions in (5) and (6). The simulation diagram is shown in Figure. 2. The state
variables will be defined as the outputs of the integrators, with x1 being ia, x2 being θ,
and x3 being dθ/dt.
dia(t) /dt = − (Ra/ La )¶ ia(t) – (Kb /La ¶) dθ(t) /dt + ( 1 /La )¶ Va(t) (5)
d^2θ(t)/ dt^2 = − (B/ J) ¶ dθ(t)/ dt + (KT/ J) ¶ ia(t) (6)
Figure 4.9 Simulation Diagram for The DC Servo Motor
Example With these definitions for the state variables, and defining
u(t) = Va(t) and y(t) = θ(t), the state and output equations are:
x1(t) = − (Ra/ La )¶ x1(t) – (Kb/ La )¶ x3(t) + ( 1/ La )¶ u(t) (7)
x2(t) = x3(t) (8)
x3(t) = − (B /J )¶ x3(t) + (KT /J) ¶ x1(t) (9)
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y(t) = x2(t) (10)
In short hand notation, the state and output equations are :
x(t) = Ax (t) + Bu (t), y (t) = Cx (t) (11)
4.5 Potentiometers
A Potentiometer is a variable resistor. The two output terminals act as a fixed
resistor. A movable contact called a wiper (or a slider) moves across the resistor,
producing a variable resistance between the center terminals and the two sides. A
potentiometer is basically a voltage divider which is used for the measurement of
potential. Potentiometers are commonly used to control electrical devices such as volume
controls on audio equipment. Potentiometers which are operated by a mechanism can
also be used as position transducer.
Figure 4.10 A Potentiometer
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A potentiometer is a manually adjustable electrical resistor that uses three
terminals. In many electrical devices, potentiometers are establishes the levels of output.
For example, in case of a loudspeaker, a potentiometer is used to adjust the volume or
taken the case of a television set, computer monitor or light dimmer; it can be used to
control the brightness of the screen or light bulb.
Figure 4.11 Circuit Diagram of a Potentiometer
4.6 Bluetooth HC-06 module
HC.06 module is an easy to use Bluetooth SPP (Serial Port Protocol) module,
designed for transparent wireless serial connection setup. Serial port Bluetooth module is
fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate) 3Mbps Modulation with
complete 2.4GHz radio transceiver and baseband. It uses CSR Blue core 04.External
single
chip Bluetooth system with CMOS technology and with AFH(Adaptive
Frequency Hopping Feature). It has the footprint as small as 12.7mmx27mm.
24
Figure 4.12 Bluetooth HC.06 module (Front View)
Figure 4.13 Bluetooth HC.06 module(Back View)
4.7 Specifications
4.7.1 Hardware features
Typical .80dBm sensitivity
Up to +4dBm RF transmit power
Low Power 1.8V Operation ,1.8 to 3.6V I/O
PIO control
UART interface with programmable baud rate
With integrated antenna
With edge connector
4.7.2 Software features
Default Baud rate: 38400, Data bits: 8, Stop bit: 1, Parity: No parity, Data
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Control: has supported baud rate:
9600,19200,38400,57600,115200,230400,460800.
Given a rising pulse in PIO0, device will be disconnected.
Status instruction port PIO1: low disconnected, high connected;
PIO10 and PIO11 can be connected to red and blue led separately. When master
and slave are paired, red and blue led blinks 1time/2s in interval, while
disconnected only blue led blinks 2times/s.
Auto connect to the last device on power as default.
Permit pairing device to connect as default.
Auto pairing PINCODE:‖0000‖ as default
Auto reconnect in 30 min when disconnected as a result of beyond the range of
connection.
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CHAPTER 5: MECHANICAL PORTION
5.1Mechanical Design
The mechanical design of the robot arm is based on a robot manipulator with
similar functions to a human arm . The links of such a manipulator are connected by
joints allowing rotational motion and the links of the manipulator is considered to form a
kinematic chain. The business end of the kinematic chain of the manipulator is called the
end effector or end of arm tooling and it is analogous to the human hand. Figure 5.1
shows the Free Body Diagram for mechanical design of the robotic arm.
Figure 5.1 Free body diagram of the robot arm
As shown, the end effector is not included in the design because a commercially
available gripper is used.This is because that the end effector is one of the most complex
parts of the system and, in turn, it is much easier and economical to use a commercial one
than build it. Figure 5.17 shows the work region of the robotic arm. This is the typical
workspace of a robot arm with four degree of freedom (6 DOF). . The mechanical design
27
was limited to 6 DOF mainly because that such a design allows most of the necessary
movements and keeps the costs and the complexity of the robot competitively
Accordingly, rotational motion of the joints is restricted where rotation is done around
two axis in the shoulder and around only one in the elbow and the wrist, see Figure 5.18.
The robot arm joints are typically actuated by electrical motors. The servo motors were
chosen, since they include encoders which automatically provide feedback to the motors
and adjust the position accordingly.
Figure 5.2 Work region of the robotic arm
28
Figure 5.3 Force diagram of robot arm
Figure 5.4 Force diagram of link CB
However, the disadvantage of these motors is that rotation range is less than 180˚
span, which greatly decreases the region reached by the arm and the possible positions
[9]. The qualifications of servo motors were selected based on the maximum torque
required by the structure and possible loads. In the current study, the material used for the
structure was acrylic.
Figure 2.16 shows the force diagram used for load calculations. The calculations
were carried out only for the joints that have the largest loads, since the other joints
would have the same motor, i.e. the motor can move the links without problems. The
calculations considered the weight of the motors, about 50 grams, except for the weight
of motor at joint B, since it is carried out by link BA. Figure 2.17 shows the force
diagram on link CB, which contains the joints (B and C) with the highest load (carry the
links DC and ED) and the calculations are carried out as follows.
The values used for the torque calculations:
Wd = 0.020 kg (weight of link DE)
Wc = 0.030 kg (weight of link CD)
29
Wb = 0.030 kg (weight of link CB)
L = 1 kg (load)
Cm = Dm = 0.050 kg (weight of motor)
LBC = 0.14 m (length of link BC)
LCD = 0.14 m (length of link CD)
LDE = 0.05 m (length of link DE)
Performing the sum of forces in the Y axis, using the loads as shown in Figure 5.20,
and solving for CY and CB, see Equations (1).(4). Similarly, performing the sum of
moments around point C, Equation (5), and point B, Equation (6), to obtain the torque e
in C and B, Equations (7) and (8), respectively.
30
The servo motor that was selected, based on the calculations, is 7 small servo with
torque: 1.8 kg/cm and one big servo with torque 10kg/cm
31
. This motors was recommended because it is much cheaper than any other motor
with same specifications. Since we need more torque at joint B, see Equation (8), we used
two motors at point B to comply with the torque requirements; however, one motor is
enough for the other joints. Using two motors at joint B is much cheaper than using one
big motor with 10kg/cm. Other relevant characteristics of the motors, which can be
shown in Figureure 5, are that they can turn 60 degrees in 130 milliseconds and they have
a weight of 47.9 grams each. Once the initial dimensions for the robot arm and the motor
were defined, the design were carried out using the SolidWorks platform; design should
Figure 5.5 Two Type of Servo Motor
carefully take into account the thickness of the acrylic sheet and the way that the pieces
would be attached to each other. The acrylic sheet used to make the robot is 1/8 thickness
And that thin sheet was chosen because it easier for machining and less weight
with a good resistance. During design, we faced some difficulties due to the way of
joining thin acrylic parts strongly. It was needed tools to burn and join the acrylic parts
and that weren’t available and the team considered that a mechanical junction based on
screws and nuts would be much strong than other alternatives, such as glue for example.
In order to accomplish this, a small feature was designed which allowed to fasten the
32
bolts with the nuts without having to screw in the thin acrylic layer. The result of this
process was the tridimensional design shown in Figure 6.21 By end of design, each part
was printed in full scale in cardboard paper and then we verified all the dimensions and
the interfaces of the assembly. In turn, we built the first prototype of the robot arm. Next,
parts of the robot arm were machined from the acrylic sheet using a circular saw and
Dermal tools. The detailing on the parts was done in a professional workshop since the
parts of robot arm were too small and it is not an easy for accomplishing such small and
accurate cuts. During assembling the robot parts with the motors, few problems pop up.
There were critical points that did not resist the fastening and, in turn, may break down;
hence, reinforcements in these points were considered. The final result of the robot arm is
shown in Figure 5.21
5.2 Driving engines using complementary angle
We use this Operation to control tow servo motors In opposite direction for each
other's. The small servo G9 we use have a rotation limit 180 degree so we command the
first servo motor to move to angle X and command the opposite servo motor to move to
angle 180.X then the tow motors well move in Synchronous movement that meets our
needs.
5.3 Robot Arm Control
The robot arms can be autonomous or controlled manually. In manual mode, a trained
operator (programmer) typically uses a portable control device (a teach pendant) to teach
a robot to do its task manually. Robot speeds during these programming sessions are
slow. In the current work we enclosed the both modes. The control for the presented
robot arm consists basically of three levels: a microcontroller, a driver, and a computer
based user interface. This system has unique characteristics that allow flexibility in
programming and controlling method, which was implemented using inverse kinematics;
besides it could also be implemented in a full manual mode. The electronic design of
control is shown in Figure 11. The microcontroller used is an Atmega 368p which comes
with a development/programming board named ―Arduino‖, as shown in Figure 12. The
programming language is very similar to C but includes several libraries that help in the
33
control of the I/O ports, timers, and serial communication. This microcontroller was
chosen because it has a low price, it is very easy to reprogram, the programming
language is simple, and interrupts are available for this particular chip. The driver used is
a eight .channel for servo controller board. It supports tow control methods: Bluetooth for
direct connection to an android device or direct control using variable resistors. This
controller, as shown in Figure 5.6.
Figure 5.6 Electronic scheme of control
5.4 End-Effector Selection
The end effector is probably one of the most important and most complex parts of
the system. The end effector varies mainly according to the application and the task that
34
the robot arm accomplishes for; it can be pneumatic, electric or hydraulic. Since our robot
arm is based on an electric system, we may choose electric basis of end effector. Besides,
the main application of our system is handling, accordingly, the recommended type of
our end effector is a gripper, as shown in Figurer 5.22 and Figurer 5.23. Please note that
the end effector is controlled by a servo motor .
Figure 5.7 gripper Closed , gripper Open
5.5 MIT App Inventor
MIT App Inventor is a blocks based programming tool that allows everyone, even
novices, to start programming and build fully functional apps for Android devices.
Newcomers to App Inventor can have their first app up and running in an hour or less,
and can program more complex apps in significantly less time than with more traditional,
text based languages. Google's Mark Friedman and MIT Professor Hal Abelson co-led
the development of App Inventor while Hal was on sabbatical at Google. Other early
Google engineer contributors were Sharon Perl, Liz Looney, and Ellen Spertus . App
Inventor runs as a Web service administered by staff at MIT’s Center for Mobile
Learning. A collaboration of MIT’s Computer Science and Artificial Intelligence
Laboratory (CSAIL) and the MIT Media Lab. MIT App Inventor supports a worldwide
community of nearly 3 million users representing 195 countries worldwide. The tool’s
more than 100 thousand active weekly users have built more than 7 million android apps.
An open source tool that seeks to make both programming and app creation accessible to
a wide range of audiences
35
Figure 5.8 MIB Structure
Formal and informal educators who have used MIT App Inventor to introduce
programming to their Computer Science students, science club members, after school
programs attendees, and summer campers. Many educators have also started to use MIT
App Inventor to develop apps in support of their own instructional objectives.
Government and civic employees and volunteers who have harnessed the power of
MIT App Inventor to develop custom, often hyper local apps in response to natural
disasters and community based needs Designers and product managers who have seen the
potential that MIT App Inventor has to support the iterative design process via rapid
prototyping, testing and iteration.
Researchers who use MIT App Inventor to create custom app in support to meet their
data collection and analysis requirements in support of their research in a wide variety of
fields from medical to social.
Hobbyists and Entrepreneurs who have an idea they want to quickly turn into an app
without the cost or learning curve that more traditional app creation entails.
5.6 Robotic arm app using MIT app inventor
We use the app inventor to create an app on android device to control on robotic
arm using android device and Bluetooth module
36
5.6.1 Interface designer :
Figure5.12 Interface designer
37
5.6.2 Interface Blocks:
Figure5.13 Interface Blocks
5.6.3 App Designer:
38
Figure 5.14 App Designer
5.6.4 Arm Block Diagram:
39
Figure 5.15 Arm Block Diagram
CONCLUSION
The main focus of this work was to design, and programme robotic arm the robot
arm was designed with five degrees of freedom and talented to accomplish accurately
simple tasks, such as light material handling the robot arm is equipped with several servo
40
motors which do links between arms and perform arm movements. A microcontroller that
drives the servo motors with the capability of modifying position
The programming is done on ATMEGA-328p Microcontroller using Arduino
programming. The potentiometers are also used to detect the angle of rotation and the
signals are then sent to the microcontroller. And you can control the robotic arm also
using android device, in today’s world, this Robotic arm has turned out very benevolent.
Besides Robotics and Automation, these kinds of arms have applications in other fields
also.
REFERENCE
41
[1] C. F. Olson, Lab. JP, Technol. CIo, Pasadena, ―Probabilistic self-localization for
mobile robots‖; IEEE Transactions on Robotics and Automation 16,1, 55-66, 2000.
[2] R.B. Gillespie, J. E. Colgate, M. A. Peshkin, ―A general framework for robot
control‖; IEEE Transactions on Robotics and Automation, 17,4, 391-401, 2001. [3]
Devendra P. Garg and Manish Kumar, ―Optimization Techniques applied to multiple
manipulators for path planning and torque minimization‖; Engineering Applications of
Artificial Intelligence 15, 3-4, 241-252, 2002.
[4] J. C. Trinkle and R. James Milgram, ―Complete Path Planning for Closed Kinematics
Chains with Spherical Joints‖; SAGE International Journal of Robotic Research 21, 9,
773- 789, 2002.
[5] M. Gemeinder and M. Gerke, ―GA-based Path Planning for Mobile Robot Systems
employing an active Search Algorithm‖; Journal of Applied Soft Computing 3, 2, 149-
158, 2003. [2]. ―Six-servo Robot Arm‖ from www.arexx.com.cn on 13-11-2011 pg: 1-18
[6]. Jegede Olawale, Awodele Oludele, Ajayi Ayodele, ―Development of a
Microcontroller Based Robotic Arm‖, in Proceedings of the 2007 Computer Science and
IT Education Conference pg: 549-557.
[7]. ―Six-servo Robot Arm‖ from www.arexx.com.cn on 13- 11-2011.
[8]. ―Robotic Arm‖ - www. NASA explores. com
[9]. ―Robot software‖ from Wikipedia, the free encyclopedia on 04-3-2012
[10]. ―ATMEL – short notes‖, www.atmel.com
[11]. ―Arduino MCU‖, - www.arduino.com
[12].―Servomotors & system design components‖, - www.bhashaelectronics. Com
[13] Robert J. Shilling "Fundamentals of robotics analysis and control ".
[14] GORDON McCOMB" The robot builders' bonanza ".
[15] www.wikipedia.com/robotic.
42
[16] G. J. Monkman" Robot Gripper ".
[17] http://www.instructables.com/
[18] J. M. Selig "Introductory Robotics"
[19] Andrease Wolf "Grippers in Motion"
[20] www.SocietyofRobots.com
43
Appendix A
#include <Servo.h>
#include <SoftwareSerial.h>
SoftwareSerial Bluetooth(10, 11);
char Serial_Data;
Servo myservo0;
Servo myservo1; // create servo object to control a servo
Servo myservo2;// twelve servo objects can be created on most boards
Servo myservo3;
Servo myservo4;
Servo myservo5;
Servo myservo6;
Servo myservo7;
const int sensor1=A0;
const int sensor2=A1;
const int sensor3=A2;
const int sensor4=A3;
const int sensor5=A4;
const int sensor6=A5;
int pos0 = 180; // variable to store the servo position
44
int pos1=90; // variable to store the servo position
int pos2=90; // variable to store the servo position
int pos3=90; // variable to store the servo position
int pos4=90; // variable to store the servo position
int pos5=90; // variable to store the servo position
int pos6=90; // variable to store the servo position
int pos7=90; // variable to store the servo position
void setup()
{
Bluetooth.begin(9600);
myservo0.attach(2);
myservo1.attach(3);
myservo2.attach(4);
myservo3.attach(5);
myservo4.attach(6);
myservo5.attach(7);
myservo6.attach(8);
myservo7.attach(9);// attaches the servo on pin 9 to the servo object
/////////////////////////////////////////////////////////////////////
}
45
void loop() {
pos0=analogRead(sensor1);
pos0=map(pos0,0,1023,0,180);
myservo0.write(pos0);
pos1=analogRead(sensor2);
pos1=map(pos1,0,1023,70,110);
pos2=analogRead(sensor2);
pos2=180-map(pos2,0,1023,70,110);
myservo1.write(pos1);
myservo2.write(pos2);
pos3=analogRead(sensor3);
pos3=map(pos3,0,1023,0,180);
pos4=analogRead(sensor3);
pos4=180-map(pos4,0,1023,0,180);
myservo3.write(pos3);
myservo4.write(pos4);
pos5=analogRead(sensor4);
pos5=map(pos5,0,1023,0,180);
myservo5.write(pos5);
46
pos6=analogRead(sensor5);
pos6=map(pos6,0,1023,0,180);
myservo6.write(pos6);
pos7=analogRead(sensor6);
pos7=map(pos7,0,1023,90,180);
myservo7.write(pos7);
if (Bluetooth.available()){
Serial_Data=Bluetooth.read();
if (Serial_Data=='X'){
for (;;){
Serial_Data=Bluetooth.read();
/////////////////////////////////////////////////
if (Serial_Data=='1'){
if (pos0<177){
pos0=4+pos0;
}
myservo0.write(pos0);
47
Serial_Data=0;
}
if (Serial_Data=='2'){
if(pos0>3){
pos0=pos0-4;
}
myservo0.write(pos0);
Serial_Data=0;
}
/////////////////////////////////////////////
if (Serial_Data=='3'){
if (pos1<109){
pos1=pos1+2;
pos2=180-pos1;
}
myservo1.write(pos1);
myservo2.write(pos2);
Serial_Data=0;
}
48
if (Serial_Data=='4'){
if (pos1>71){
pos1=pos1-2;
pos2=180-pos1;
}
myservo1.write(pos1);
myservo2.write(pos2);
Serial_Data=0;
}
////////////////////////////////////////////
if (Serial_Data=='5'){
if(pos3<175){
pos3=pos3+6;
pos4=180-pos3;
}
myservo3.write(pos3);
myservo4.write(pos4);
Serial_Data=0;
}
49
if (Serial_Data=='6'){
if(pos3>5){
pos3=pos3-6;
pos4=180-pos3;
}
myservo3.write(pos3);
myservo4.write(pos4);
Serial_Data=0;
}
////////////////////////////////////
if (Serial_Data=='7'){
if(pos5>5){
pos5=pos5-6;
}
myservo5.write(pos5);
Serial_Data=0;
}
if (Serial_Data=='8'){
if (pos5<175){
pos5=pos5+6;
50
}
myservo5.write(pos5);
Serial_Data=0;
}
//////////////////////////////////////////////
if (Serial_Data=='9'){
if(pos6<175){
pos6=pos6+6;
}
myservo6.write(pos6);
Serial_Data=0;
}
if (Serial_Data=='A'){
if(pos6>5){
pos6=pos6-6;
}
myservo6.write(pos6);
Serial_Data=0;
}
/////////////////////////////////////////
51
if (Serial_Data=='B'){
if (pos7<175){
pos7=pos7+6;
}
myservo7.write(pos7);
Serial_Data=0;
}
if (Serial_Data=='C'){
if (pos7>95){
pos7=pos7-6;
}
myservo7.write(pos7);
}
}}}}}